Surface grinders



Filed June 6, 1960 3 SheetsSheet 1 FIG! FIGIA I w Afro/1min:

Jan. 15, 1963 J. SELBY SURFACE GRINDERS 3 Sheets-Sheet 2 Filed June 6, 1960 If: IEIIIIIII' FIG- 2 R WW 2M #5 w 2 a M I Jan. 15, 1963 J. SELBY 3,073,072

SURFACE GRINDERS Filed June 6, 1960 3 Sheets-Sheet 5 FIG..

INVENTOR In): 551.8%

flrranuzrs 3,'d73,@72 Patented Jan. 15, 1963 3,073,072 dURFACE GRINDERS James elhy, Hatch End, England, assignorto B..-Eiliott 3: Company Limited, London, England, a British company F'ied June 6, 196%, Ser. No. 34-,llii6 Z2 tClaims. (Cl. 51-?2) tion relative to a base, wherein said machine has a con-' trol system whereby either both the saddle and the worktable are reciprccated, whereby criss-cross'grinding is eifected, or one of said parts (hereinafter, for con-- venience, assumed to be the work-table) is reciprocated, whilst the other part (hereinafter, for convenience, assumed to be the saddle) is moved step by step unidirectionally, whereby step by-step grinding is effected.

in order that the invention may bethe more clearly understood, a machine in accordance therewith will now be described, reference being made to the accompanying drawings, wherein:

FIGURE 1 is a somewhat diagrammatic front elevation of the machine.

FIGURE lAis a fragmentary plan view of FIG- URE 1.

FlGURE 2 is a somewhat diagrammatic side elevation of the machine.

FIGURE 3 is a hydraulic circuit diagram illustrating the operation of the machine.

Referring first to FIGURES l and 2 the spindle 1 of the grinding wheel 2 rotates in a bearing carried near the upper end of a wheel head assembly 3.which is mounted on the rear external surface of a cast boxshaped base 4 so as to be slidable up and down. Said spindle 1 extends horizontally so that the grinding wheel 2 overhangs the top surface of said box-shaped base.

On said top surface of the box-shaped base is mounted a saddle b which reciprocates in a direction parallel to the axis of the grinding wheel spindle l, and, mounted on the top of said saddle is an elongated work-table d which reciprocates longitudinally, that is atright angles to the axis of the grinding wheel spindle. By adjusting the Wheel head assembly 3, the grinding wheel 2. can be adjusted to the appropriate height for grinding the surface of a given workpiece on the work-table d, and the grinding is then effected as required by making longitudinal and transverse movements with the work-table d and saddle b respectively.

Both of these movements are effected hydraulically. The movement of the saddle [2 relative to the base 4' is effected'by means of a hydraulic cylinder at which is fast with said saddle and whose piston a1 is connected by its piston rod to said base 4 at 5. Thernovement of the table d relative to the saddle b. is effected by means ofa hydraulic cylinder 0, which, like the cylinder a, is also fast with saidsaddle, and whose piston 02 is connected by its piston rod to said table at point .6.

The movement of the saddle b and the tabled may be controlled in either of two different ways selectively. According to one way (hereinafter called step-by-step control) the table d is repeatedly rreciprocated and at each reversal, or each alternate reversal, of said'table, the saddle b makes a small increment of cross traverse movement. According to the other way (hereinafter called criss-cross control) the 'saddleb, as well as the table d, is continuously reciprocated so that crisscross Thus, when step-by-step grinding is to be carried out, liquid is injected alternately intoopposite ends of the table cylinder to cause the piston, throughv its full stroke,

grinding is effected.

c2 to reciprocate continuously and a metered quantity of liquid is injected mto the saddle cylinder a at each reversal of the piston c2 of- When criss-cross grinding isto be carried out, liquid is injected alternately into'oppositeends of the saddle cylinder a to cause it to reciprocate:

the table cylinder.

continuously through its full stroke, the table cylinder 0 being controlled as before.

The control system by'which the above is effected is illustrated in FIGURE 3 and will now be described. Thus, referring to FlGURE 3, two separate sourcesv of hydraulic supply e and f are provided for the saddle:

cylinder at and the table cylinder 0 respectively. These sources may consist, as shown, of respective gear pumps which take in from a tank g. When the system is set;

for criss-cross grinding, the table cylinder 0 is continuously reciprocated by liquid from the supply The hydraulic system for this form of grinding is straightforward and need only be described briefly.

Thus, for driving the table cylinder 0, liquid flows from source 1 to a port hi of a rotary direction-reversillustrated, the liquid will flow from said rotary direc-- (ion-reversing valve through a port I12 thereof and thence to a port ii at one end of the cylinder of a piston type direction-reversing relay valve i. Said direction-reversing relay valve i will therefore be at the end of its stroke opposite to its Port i1 as illustrated. The other end of said cylinder of the direction-reversing relay valve is connected, by way of a port i2 therein to a port I13 of said rotary direction-reversing valve, and from thence through a port h4- of the latter to exhaust in the tank g, and thus the direction-reversing relay valve i was free to move to its illustrated position when the rotary direction reversing valve h was first moved to its illustrated position.

The direction-reversing relay valve i being at its illus trated position, liquid flows from the source 1 to a port 1'1 of a rotary control valve 1 and from a. port '2 of said rotary control valve to a port iii of said direction-reversing relay valve i, and out from a port id of the latter to a port cl at one end of the table cylinder c. The piston 02 of said table cylinder is accordinglydriven towards. the opposite end of said table cylinder. At the sametime, liquid on the other side of said piston 02 is free to flow out of a port c3 in the opposite end of said table cylinder through a port in the cylinder of the direction-reversing relay valve i and out through a port id in said last-named cylinder to exhaust in the tank 3. 7

When said piston 02 reaches the end of the table cylinder 0 having the port c3 therein, the rotary direction-reversing valve h is turned to its non-illustrated position. Liquid from the source 7 now flows through port hl of said rotary direction-reversing valve and out from the port I23 thereof to said port i2 of said direction-reversing, rela valve. At the same time the port it of said directionreversing relay valve is connected, through the ports b2, and he of the rotary direction-reversingvalve, to exhaust at the tank g. Said direction-reversing relayvalve accordingly moves to its non-illustrated position.

Said direction-reversing relay valve i being at its nonf, and thesaddle cylinder a is continuously reciprocated by liquid from the supply 6, and the two cylinders being driven independently and without being in any way synchronised.

illustrated position, liquid flows from the source f, in through the port jl and out through the port '2 or" the rotary control valve 1', to the port i3 of the direction-reversing relay valve. This latter port i3 is now connected to the port i5 of said direction-reversing relay valve and therefore to the port 03 of the table cylinder. At the same time the port id of the direction-reversing relay valve is now connected to a port i7 of said relay valve which is permanently connected to exhaust at the tank g, and therefore the port cl of the table cylinder is connected through the port i4 and i7 of the direction-reversing relay valve to exhaust. The piston of the table cylinder there fore returns to the end of said cylinder having the port 01 therein.

The rotary direction-reversing valve [1 therefore returns to its illustrated position, so that the piston 02 of t.e table cylinder c returns to the end of said table cylinder having the port c3 therein and so on.

A relief valve k is provided whereby, if the delivery pressure of the source exceeds a given value the liquid from said source returns direct to exhaust in the tank g.

An adjustable throttle valve 1 is provided between the port i2 of the direction-reversing relay valve and the port I23 of the rotary direction-reversing valve, whereby alternately the pressure flow, or the exhaust flow, through said last-named port P23 is controlled, and therefore the speed of movement of said relay valve 1' is controlled.

For driving the saddle cylinder (1, liquid flows from the source 2, in through a port 1121 and out through a port m2 of a rotary control valve in, and thence in through a. port n1 and out through a port n2 of a rotary change-over valve n, which is now assumed to be at the position illustrated which is the position for criss-cross control, and thence in through a port 01 in the wall of the cylinder of a piston-type direction-reversing valve 0, which is adapted to reverse its position each time the saddle reaches the end of its stroke. The reversal of the valve is controlled by dogs 13 which should be visualized as being adjustable in reference to a base in the axial direction of valve 0. If said direction-reversing valve is assumed to be at the illustrated position, the liquid will flow through said port 01 and a port 02 to a port a2 at one end of the saddle cylinder a. At the same time liquid on the other side of the piston al of said saddle cylinder is free to flow out of a port a3 in the opposite end of said saddle cylinder, in through a port 03 in the cylinder wall of said direction-reversing valve 0, and out through a port 04 in said cylinder wall to exhaust in the tank g. The saddle cylinder a is accordingly driven towards the end of its stroke at which the port a3 is ad acent to the piston a1.

When said cylinder reaches this end of its stroke, the direction-reversing valve 0 is moved to its non-illustrated position. Liquid from the source e now flows, as previously traced, in through the port 01 of the cylinder of said longitudinal direction-reversing valve, and out through the port 03 of said cylinder to the port (13 of the saddle cylinder. Also the liquid in said saddle cylinder is free to flow out through the port a2 thereof, and in through the port 02 of the cylinder of the directionreversing valve 0 and out through a port of said lastnamed cylinder to exhaust. The saddle cylinder will accordingly be driven back to the illustrated position.

.This will cause the direction-reversing valve 0 to be returned to its illustrated position, so that the saddle cylinder returns to the non-illustrated position and so on.

There is also a relief valve p whereby, if the delivery pressure of the source e for the saddle cylinder exceeds a given value, the liquid from said source returns direct to exhaust.

Describing now the system of control for step-by-step grinding, the control of'the table cylinder is, of course, the same as in the case of criss cross grinding. For the control of the saddle cylinder, two additional valves are employed, both of the piston type, in which the valve reciprocates in a cylinder, viz. a table-responsive valve q and a metering valve r.

The cylinder of the table-responsive valve q has two ports ql and q2 in its two ends which are respectively connected to the two ports i1 and i2 in the ends of the cylinder of the direction-reversing relay valve 1', so that said table-responsive valve q is slave to said directionreversing relay valve i. Thus said table-responsive valve q is at its illustrated position when the direction-reversing relay valve i at its illustrated position and at its nonillustrated position when said direction-reversing relay valve is at its non-illustrated position.

The metering valve r consists simply of a cylinder with a loose piston rl therein and two ports r2; and r3 adjacent its two ends on each side of said piston.

For changing from criss-cross grinding to step-by-step grinding, the aforesaid change-over valve i1 is moved from its illustrated position for criss-cross control to its position for step-by-step control. This cuts olf the port 111 from the port n2 of said changeover valve, and thereby cuts off the previously traced path from said source 2 to the port 01 of the direction-reversing valve 0. Said movement of said change-over valve it also connects a port n3 to a port 124 thereof, and thereby establishes communication from the source to two ports (13 and g4 in the side of the cylinder of the table-responsive valve q.

Assuming that the direction-reversing relay valve i is at its illustrated position so that the piston 02 of the table cylinder is travelling towards the end of said cylinder having the port c3 therein, said table responsive valve q will also be at its illustrated position and consequently the port q3 in its cylinder wall will be connected to a port g5 in said cylinder wall which port q5 is connected to the port r2,in the cylinder wall of the metering valve r. Consequently the source will be connected, through said ports q3 and 5 of the table-responsive valve to the port r2 or" said metering valve, and the piston r1 of said metering valve will be maintained at the end of its stroke towards the port r3 of said metering valve. Said port r3 of the metering valve is connected to a port qd of the table-responsive valve, and, the latter valve being at its illustrated position, said port qd is connected to a port q7 of said table-responsive valve which port q7 is connected to the aforesaid port 01 of the direction-reversing valve 0, and, assuming that this last valve is at its illustrated position, said port 01 thereof is connected to the port 02 thereof which is connected to the port a2 of the saddle cylinder a.

The port r3 of the metering valve is thus connected to the port a2 of the saddle cylinder and in this way said saddle cylinder is being retained at the point of its stephy-step advance which it"has already reached. The port a3 of said saddle cylinder is connected, through the ports 03 and 04 of the direction-reversing valve 0, to exhaust.

When the piston 02 of the table cylinder reaches the end of said cylinder having the port (:3 therein, the tableresponsive valve q will move to its non-illustrated position, and the port g4 thereof will be connected to the port :76 thereof and thence to the port r3 of the metering valve. The source will therefore be connected to said port r3 of the metering valve.

Also the ports g5 and q7 of the table-responsive valve will be connected together so that the port r2 of the metering valve will be connected, through said ports g5 and q7 of said table-responsive valve to the port all of the longitudinal direction-reversing valve, which is still at its illustrated position and thence, as previously traced, to the port a2 of the saddle cylinder.

Thus the port r2 of the metering valve is connected to the port a2 of the saddle cylinder, and, as the port r3 of said metering valve is connected to the source e, the piston r1 of said metering valve will therefore make its stroke towards the port r2 of said metering valve, and a measured quantity of liquid will be driven into the saddle cylinder a through the port n2 thereof, and said saddle cylinder will make a step of movement towards the end (if its stroke at which the port a3 is adjacent the piston a When thepiston c2 of the table cylinder c again reaches the endof said-cylinder having the port c1 therein, the table-responsive. valve q will again move to its illustrated position, and thus the source e will be again connected to the port r2 of the metering valve and the port'rS' of said metering valve will be again connected to theport Q2 of the saddle cylinder. The piston rii ofsaid metering valve will accordingly make its stroke towards the port r3 thereof and a further'metered quantity of the liquid will be driven into the saddle cylinder through the port 112 thereof, and thesaddlecylinder will make a further increment-of movement towards the end of its stroke at which the port a3 is adjacent to the piston a l."

It will thusbe seen that this incremental movement of the saddle cylinder-will continue step-by-step each time the piston c2 of the table cylinder reaches anend of its stroke, until the saddle cylinderreaches the end of its stroke at which the port a3 is adjacent the piston all. When this happens, the direction-reversing valve 0 is moved to its non illustrated position, and the saddle cylinder now .makes incremental movements towards the end of its stroke at which the port :12 is adjacent the piston a1.

Thus, when said direction-reversing valve 0 is at its non-illustrated position,.the port 01 thereof is connected to the port 03 thereof and thence to the port Q3 of the saddle cylinder, and port 02 of said direction-reversing valve is connected to the port 05 thereof and therefore the crt aZ of the saddle cylinder is connected to exhaust. Therefore the action is the same as before except that the measured quantity of liquid is each time supplied to the saddle cylinder, through'port a3 thereof, and the port a2 thereofis connected to exhaust. The saddle cylinder therefore now makes steps in the direction towards the end of its stroke which is illustrated.

To sum up, each time the table a is reversed, the saddle 12 makes .a small step of movement and these steps continue in the same direction until the saddle has completed its predetermined stroke in that direction, whereupon the steps takes place in the opposite direction until the saddle stroke is completed in said opposite direction, and so on.

In order that the extent of each step of movement of the saddle may be varied, means are provided for varying the stroke of the piston r1 of the metering valve r. This means may consist simply of an adjustable screw threaded stop r4.

In the above description, the rotary control valves 1' and m have been assumed to occupy the illustrated position throughout. It will be readily seen that, by moving the control valve 1' to its non-illustrated position, at which the port jl is cut off from the port '2 and is connected to the port j3, the source is connected directly to exhaust and the table drive ceases .to operate. In like manner, by moving the control valve m to its non-illustrated position at which the port m1 is cut off from the port m2 and is connected to the port m3, the source e is connected directlyto exhaust, and the saddle drive ceases to operate.

Returning to FIGURES 1 and 2, a valve block 7 is provided, fast with the saddle b, in which all the valves illustrated in FIGURE 3 are contained. As both cylinders a and c are also fast with the saddle b, the conduits to said cylinders need not be flexible. The tank g is located in the base 4 andso also. are the ,two gear pumps 2 and j, which are incorporated with an electric drivingmotor in a unit 8 (FIGURES 1 and 2). It will thus beseen that the conduits leading from said gear pumps e and f to the valve system, and also the exhaust conduit leading from the valve system to the tank, must be flexible but otherwise none of the conduits shown in FIGURE 3 need be flexible.

The only valves which have to be operated by hand are i, m, l and n. The control knobs for these valves, which are not shown, are, of course, mounted on the outside of the valve block 7. The stroke of the metering valve r is also controllable by hand and its control knob is'mounted on the outside of the valve block 7 The reference 9 designates an electric motor which is incorporated in one structure with the wheel head assembly 3 and drives the spindle 1 of the grinding wheel through a belt or chain drive 10.

The manual controls for adjusting the wheel head assembly 3, and those also for adjusting the saddle b and work-table d when they are cut off from hydraulic control, are conventional and have not been illustrated or described.-

The particular construction and arrangement described and arranged above may obviously be modified in many ways without departing from the scope of the invention.

I claim:

1. A surface grinding machine comprisinga base, a

saddle movably mounted on said base, a table movably mounted on said saddle, a first reversible hydraulic means operatively coupled to said table for reciprocating move-' ment thereof inone direction from an extreme position;

a second reversible hydraulic means operatively coupled to said saddle for reciprocating movement thereof in a direction transverse to said table, means for automatically reversing the direction'of movement of the saddle at each end of its stroke, adjustable valve means for-controlling the movement of said saddle with respect to said table, in

one position of said valve means said saddle being movable in said transverse direction reciprocatingly concurrent with the reciprocation of said table, in another position of-said valve means said saddle being movable in said transverse direction in at least one separate step whensaid table is at said extreme position along a displace path.

2. A grinding machine according to claim 1, wherein said adjustable valve means is a unitary control element having one position for criss-cross grinding and another position for the step-by-step grinding.

3. A grinding machine according to claim 1, wherein said table and said saddle are driven by respective reversible hydraulic motors each of which includes a cylinder and a piston.

4-. A surface grinding machine comprising a base, a saddle movably mounted on said base for reciprocating movement relative thereto in one direction, a table movably mounted on said saddle for reciprocating movement relative thereto in a direction transverse to said one direction, a first reversible hydraulic motor operatively coupled to said table, a first hydraulic fluid supply circuit for said first motor, table reversing valve means connected in said first circuit for reversing the direction in which said first motor is driven when said table is at an extreme position, a second reversible hydraulic motor operatively coupled to said saddle, a second hydraulic fluid supply circuit for said second motor, saddle reversing valve means in said second circuit for automatically reversing the direction in which said second motor is driven, an increment feed valvein said first and second circuits for controlling the quantity of fluid in said second circuit when said table is at said extreme position to move saidsaddlein separate steps, and control means for selecting the operable periods of said increment feed valve and said saddle reversing valve means-to provide movement of said table and said saddle reciprocating separately and concurrently together, respectively, forstep-by-step and criss-cross grinding.

5. A grinding machine according to. claim 4, wherein for criss-cross grinding the supply of fluid for said first motor. is controlled by direction-reversing valve means which is responsive to the 'position'of the said table so that said table is continuously reciprocated, and the supply of fiuidfor said saddle motor is controlled by said saddlereversing valve means, which is responsive to the position of he saddle so that said saddle is continuously reciprocated.

6. A grinding machine according to claim 5, wherein said direction-reversing valve means includes a directionreversing valve controlled according to the position of G said table, and a direction-reversing relay valve which is controlled hydraulically by said direction-reversing valve and which controls the said first motor.

7. A grinding machine according to claim 6, wherein an adjustable throttle valve controls the speed of movement of said direction-reversing relay valve.

8. A surface grinding machine comprising a base, a saddle movably mounted on said base for reciprocating movement relative thereto in one direction, a table movably mounted on said saddle for reciprocating movement relative thereto in a direction transverse to said one direction, a first reversible hydraulic motor operatively coupled to said table, a first hydraulic fluid supply circuit for said first motor, a table reversing valve connected in said first circuit for reversing the direction in which said first motor is driven by the fluid of said first circuit when said table arrives at its extreme positions in its reciprocating movement in said one direction, a second reversible hydraulic motor operatively coupled to said saddle, a second hydraulic fluid supply circuit for said second motor, a saddle reversing valve connected in said second circuit operable to reverse the direction in which said second motor is driven by the fluid of said second circuit, means responsive to the arrival of the saddle in its extreme positions to efiect operation of said saddle reversing valve, an increment feed valve means allowing a quantity of fluid to flow into said second circuit when said table is at its extreme positions, and control means for operating said increment feed valve means and said responsive means to provide selective movement of said table and said saddle reciprocating separately and concurrently together, respectively, for step-by-step and criss-cross grinding.

9. A grinding machine according to claim 8, wherein for step-by-step grinding the supply of liquid for said first motor is controlled by direction-reversing valve means which is responsive to the position of said table so that said table is continuously reciprocated, and the supply of liquid for said saddle motor is controlled step-by-step by said increment feed valve means so that said saddle motor is driven step-by-step in said transverse direction.

10. A grinding machine according to claim 9, wherein said increment feed valve means includes a metering valve having two ports, and means for connecting said two ports alternately to a source of hydraulic fluid and for connecting the other of said ports to a port of the saddle motor, said metering valve being such that the connection of each port to said source ejects a metered quantity of the fluid from the other of said ports, whereby metered quantities of the liquid are injected successively through said port of the saddle motor and said saddle motor is driven step-by-step in said transverse direction.

11. A grinding machine according to claim 0, wherein in response to the saddle motor reaching the end of its run in said transverse direction, the step-by-step supply of liquid to said saddle motor is adapted to drive said saddle motor step-by-step in a reverse direction.

12. A grinding machine according to claim 10, wherein said saddle reversing valve means is operable to change the injection of the metered quantities of liquid from the said port of the saddle motor to another port of said saddle motor.

13. A grinding machine according to claim 10, wherein said increment feed valve means further comprises means .for controlling the flow of fluid to and from said metering valve, the last said means comprising a reciprocating meter-control valve having one position at which one port of said metering valve is connected to said source and the other of said ports is connected to said port of said saddle motor and another position at which the other of said ports of said metering valve is connected to said source and said one port is connected to said port of the saddle motor.

14. A grinding machine according to claim 13 further comprising a direction reversing relay controlled hydraulically by said direction reversing valve means, said meter control valve being hydraulically coupled to said direction reversing relay so as to reciprocate in synchronism therewith.

15. A grinding machine according to claim 13, wherein said meter control valve reciprocates in synchronism with the reciprocation of said table.

16. A grinding machine according to claim 9, wherein the step-by-step supply of fluid to the saddle motor is controlled according to the position of the table so as to synchronise with reciprocation of said table.

' 17. A grinding machine according to claim 12, wherein said saddle-reversing valve means are connected between said meter control valve and said saddle motor.

18. A grinding machine according to claim 8, wherein separate sources of hydraulic supply are provided for said table motor and said saddle motor.

19. A grinding machine according to claim 18, wherein each of said sources includes a pump.

20. A grinding machine according to claim 8, wherein the respective hydraulic motors include cylinders with pistons, said saddle cylinder and said table cylinder are secured to said saddle, said piston of said saddle cylinder being secured to said base, said piston of said table cylinder being secured to said table, and said valve means is secured to said saddle thereby minimising the number of flexible conduits required. 7 21. A grinding machine according to claim 4, wherein said control means is a unitary control element having a changeover valve for directing a fluid flow from a source selectively to said increment feed valve for step-by-step grinding and to said saddle reversing valve means for criss-cross grinding respectively.

22. A surface grinding machine comprising a base, a saddle mounted on said base, a table movably mounted on said saddle, a first reversible hydraulic means operatively coupled to said table for reciprocating movement of the table along one direction, means automatically reversing the direction of movement of the table at each end of its stroke, a second reversible hydraulic means operatively coupled to said saddle for concurrent and continuous reciprocating movement thereof in a direction transverse to the table, increment feed means automati cally moving the saddle a partial distance of its stroke corresponding to step-by-step feed in response to the table arriving at each end of its stroke, reversing means automatically reversing the direction of movement of the saddle at each end of its stroke to provide criss-cross grinding, and control means controlling the period of operation of said increment feed means and said reversing means to provide selectively step-by-step grinding and criss-cross grinding.

References Cited in the tile of this patent UNITED STATES PATENTS 827,993 Peirce Aug. 7, 1906 2,022,542 Flygare et a1 Nov. 26, 1935 2,068,529 Baldenhofer Jan. 19, 1937 2,127,877 Maglott Aug. 23, 1938 2,269,697 Silven Jan. 13, 1942 2,671,294 Cornell Mar. 9, 1954 

1. A SURFACE GRINDING MACHINE COMPRISING A BASE, A SADDLE MOVABLY MOUNTED ON SAID BASE, A TABLE MOVABLY MOUNTED ON SAID SADDLE, A FIRST REVERSIBLE HYDRAULIC MEANS OPERATIVELY COUPLED TO SAID TABLE FOR RECIPROCATING MOVEMENT THEREOF IN ONE DIRECTION FROM AN EXTREME POSITION, A SECOND REVERSIBLE HYDRAULIC MEANS OPERATIVELY COUPLED TO SAID SADDLE FOR RECIPROCATING MOVEMENT THEREOF IN A DIRECTION TRANSVERSE TO SAID TABLE, MEANS FOR AUTOMATICALLY REVERSING THE DIRECTION OF MOVEMENT OF THE SADDLE AT EACH END OF ITS STROKE, ADJUSTABLE VALVE MEANS FOR CONTROLLING THE MOVEMENT OF SAID SADDLE WITH RESPECT TO SAID TABLE, IN 